/Engine/Source/Editor/ViewportInteraction/Public/ViewportWorldInteraction.h
Adds an actor to the list of actors to never allow an interactor to hit in the scene. No selection. No hover. There's no need to remove actors from this list. They'll expire from it automatically when destroyed.
void AddActorToExcludeFromHitTests ( [AActor](API\Runtime\Engine\GameFramework\AActor) * ActorToExcludeFromHitTests )